from abc import ABC, abstractmethod

# 定义一个抽象基类，类似于接口
class Animal(ABC):
    @abstractmethod
    def sound(self):
        """所有继承 Animal 的类都必须实现这个方法"""
        pass

    @abstractmethod
    def move(self):
        """所有继承 Animal 的类都必须实现这个方法"""
        pass

# 实现 Animal 抽象基类的具体类
class Dog(Animal):
    def sound(self):
        return "Woof!"

    def move(self):
        return "Running on four legs"

# 实现 Animal 抽象基类的具体类
class Bird(Animal):
    def sound(self):
        return "Tweet!"

    def move(self):
        return "Flying"

# 测试
animal = Bird()
print(animal.sound())
print(animal.move())